Abstract
Room temperature iron doped II-VI lasers have demonstrated broad band tunability between 3.5 and 6 μm with efficiency ~40%. However, these lasers require pump sources with a wavelength ~3 μm which could be selected only from a few available. Cobalt ions in the II-VI materials have strong absorption bands at 4 A 2 → 4 T 1 ( 4 P) and 4 A 2 → 4 T 1 ( 4 F) transitions located at ~0.75 and 1.5 μm, respectively. A number of different laser sources (including diode lasers) could be potentially used for cobalt excitation followed by energy transfer to iron ions. Here we report materials fabrication and study of energy transfer in Co:Fe:ZnS(ZnSe) crystals. Iron-cobalt co-doped samples were prepared using a two-stage post-growth thermal diffusion procedure with Fe concentrations of 8.5-19x10 18 cm -3 . Kinetics and photoluminescence spectra reveal energy transfer under cobalt excitation at 4 A 2 - 4 T 1 ( 4 F) transition by 1.56 μm radiation and 4 A 2 - 4 T 1 ( 4 P) transition by 0.7 μm radiation. Analysis shows effective energy transfer from 4 T 1 ( 4 F), 4 T 2 and 4 T 1 ( 4 F) Co 2+ energy levels to 5 T 2 excited level of Fe 2+ ions the first realization of Fe 2+ ions lasing at 3.6 μm and 3.8μm via Co-Fe energy transfer. Demonstrated effective Co 2+ →Fe 2+ energy transfer process could result in utilization of a more convenient laser pump sources for the Fe 2+ :II-VI lasers.
Published Version
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